The invention relates to an application head for contract free application of liquid media, such as thermoplastic plastics or melted hot-melt adhesives, to a width of material which is movable relative to the application head. The application head has a housing with a control slide chamber in the housing. The control slide chamber supports a cylinder control slide which is rotatingly drivable in the housing. At least one supply aperture introduces a medium into the control slide chamber in the housing. A slotted nozzle to release the medium is coupled with the housing. The slotted nozzle is controllable by the cylinder control slide. The slotted nozzle extends transversely to the direction of movement of the width of material.
An application head is shown in German 197 14 029.7. Here, a control slide is in an axial region containing the supply aperture. The control slide is provided with a recess which extends over the entire circumference. At least in the axial region, it is not possible to arrange an exit nozzle aperture which is controlled by the control slide. This means that, in the axial region, the exit nozzle apertures have to observe an undesirably large distance. In addition, the control slide is relatively short. If the control slide had a greater length, it would be necessary to provide a plurality of supply apertures. Thus, the above-referenced problem would occur several times along the slotted nozzle.
U.S. Pat. No. 5,145,689 illustrates applying adhesive from slotted nozzles where air is directed toward the medium which leads to swirling of the emerging adhesive threads. This prevents adhesive threads from tearing off and also prevents the formation of drops which could lead to a non-uniform application of adhesive. Due to the supply air, the application heads become complicated and expensive.
Application heads of the above-mentioned type find frequent application where widths of material have to be laminated onto a substrate. To minimize the specific consumption of liquid medium and, at the same time, to ensure as uniform a distribution of the medium as possible, the medium is applied intermittently to achieve a grid-like application pattern. In order to enable, at the same time, a high transport speed of the width of material, the medium has to be applied in the direction of movement of the width of material at a high frequency. The grid points extend transversely to the direction of movement of the width of material and are arranged as closely as possible to one another.
EP 0 474155 A2 and EP 0 367985 A2 illustrate application heads where hole type nozzles are controlled by a pneumatically operated nozzle needle. The medium cannot be applied economically to the width of material when it moves at a high speed. This is due to limited maximum cycle frequency of the nozzle units. This limitation is the result of the mass inertia of the nozzle needles and of the control elements.
It is therefore an object of the present invention to provide an application head of the above-mentioned type which, even if it has a great length, it is able to achieve an extremely dense application pattern.
The objective is achieved by a cylinder control slide with the following characteristics. The cylinder control slide has an inner cavity which can be supplied with medium through a supply aperture; a cylindrical surface which can seal the slotted nozzle from the inside; surface grooves in the cylindrical surface which, as a function of their rotational positions, are able to communicate with the slotted nozzle; and radial exit bores extending from the inner cavity into the surface grooves.
The inventive application head is advantageous because medium control takes place directly at the slotted nozzle. Thus, the dispensing accuracy cannot be adversely affected by the toughness of the medium or the elasticity of the medium behind the control region. By supplying the slotted nozzle with medium from the inside of the cylinder control slide, exit apertures are arranged across the entire length of the cylinder control slide. The exit apertures are at the shortest possible distance without the possibility of any interference. By selecting different shapes of the surface grooves, it is possible to produce different grids and patterns when applying the medium.
According to a first embodiment, the surface grooves include a plurality of axis-parallel grooves. If a uniform point grid is to be achieved, a plurality of axis-parallel surface grooves are provided at uniform circumferential distances on the surfaces of the cylinder control slide. The distances between the grid points in the direction of movement of the width of material can be influenced by changing the rotational speed of the cylinder control slide. If the surface grooves are circumferentially distributed at non-uniform distances, a non-uniform point grid can be produced at a constant driving speed. If the axis-parallel surface grooves are arranged at uniform circumferential distances, a non-uniform point grid can be achieved by changing the driving speeds of the cylinder control slide. State of the art servomotors are capable of operating at non-uniform driving speeds.
Grid points which extend transversely to the direction of movement of the width of material can be achieved by using a suitable nozzle orifice plate in the slotted nozzle. The individual bores are spaced at short distances. If such a nozzle orifice plate is not used, the use of axis-parallel grooves leads to a linear application transversely to the direction of movement of the width of material.
According to a second embodiment, the surface grooves include at least one helical or spiral-shaped groove. Accordingly, open regions occur at the slotted nozzle. The open regions move along the slotted nozzle during driving of the cylinder control slide in one rotational direction. Thus, if the width of material moves at the same time, application patterns occur which extend diagonally across the width of material. In this embodiment, it is preferable to use slotted nozzles without nozzle orifice plates. Thus, the diagonal applications are applied to the width of material in the form of threads. In such a case, it is advantageous to use two application heads arranged one behind the other. The heads have oppositely directed surface groove pitches with identical rotational directions of movement or opposed rotational directions of movement and identical pitches. Thus, the heads make it possible to produce a pattern of diagonal symmetric threads of medium intersecting one another on the width of material.
In one embodiment, the cylinder control slide includes at least one journal which axially projects from the housing. An axial bore is formed in the housing and is connected to the inner cavity serving as a supply aperture. This measure makes the housing design particularly simple. However, a rotating seal is provided in the region of the medium supply means subjected to pressure. According to an alternative embodiment, at at least one end of the housing, a bore is provided in the housing. Also, an annular channel is between the cylinder control slide and the control slide chamber. The annular channel is connected to the bore in the housing. Radial supply bores are provided in the cylinder control slide in the plane of the annular channel. The bores are connected to the inner cavity and serve as supply apertures. As a result of this measure, it is possible to simplify the control slide bearing. The medium can be supplied to the housing via simple radial bores. The annular channel can be formed by an annular groove in the cylinder control slide surface and/or by a circumferential groove in the control slide chamber bore. The annular channel can also be arranged in the region of the end faces of a cylinder control slide being reduced at the journals. Here, the radial supply bores are replaced by axial supply bores in the end faces. Independently of whether supply means are provided at only one end or at both ends of the cylinder control slide, it is possible to compensate for a slight pressure loss in the medium along the length of the control slide by slightly increasing the diameter of the radial exit bores leading to the grooves. The medium is prevented from escaping from the housing by using conventional shaft seals.
Furthermore, the objective is achieved by the cylinder control slide having the following characteristics. The cylinder control slide has a cylindrical surface which can seal the slotted nozzle from the inside; at least one helical or spiral-shaped surface groove in the cylindrical surface which, as a function of its rotational position, in certain portions, is able to communicate with the slotted nozzle; and a storage volume for medium inside the control slide chamber, which storage volume communicates with at least one surface groove.
At the points of intersection between the slotted nozzle and the convolution of the spiral-shaped surface groove, the inventive application head generates exit apertures which move in one direction along the nozzle slot when the cylinder control slide rotates. As a result, when the drive of the cylinder control slide rotates and when the width of material is simultaneously driven in the direction of movement, an infinite number of parallel threads are produced which extend diagonally to the direction of movement in the width of material. In consequence, the medium is applied continuously in the longitudinal direction of the width of material. The thread thickness can be kept very small. A very close application pattern is achieved with a slight pitch of the spiral-shaped surface groove and a plurality of convolutions. In an advantageous embodiment, two application heads are provided which are arranged one behind the other. The cylinder control slides of the application heads are driven in identical rotational directions and have oppositely directed surface groove pitches or, if the surface grooves have identical pitches, include oppositely directed driving rotational directions of the cylinder control slides. If both application heads are actuated and supplied with medium at the same time, a web of intersecting diagonal threads is formed on the width of material.
According to a first embodiment, the control slide chamber, in at least one circumferential region, is widened relative to the cross-section of the cylinder control slide. The widened cavity between the wall of the control slide chamber and the surface of the cylinder control slide forms the storage volume. This embodiment has both a simple housing shape and a simple shape of the solidly produced cylinder control slide. The distances between the individual exit apertures and the storage volume are extremely short and are formed by the individual contours of the surface groove.
According to a second embodiment, the cylinder control slide includes an inner cavity. The inner cavity forms the storage volume. The control slide chamber surrounds the cylinder control slide substantially sealingly with a cylindrical surface. The radial bores lead from the inner cavity into the surface groove. The variant described here is advantageous in that the surface groove is radially supplied with medium over an extremely short distance. The transport of material in the longitudinal direction of the surface groove is completely eliminated. Precision control of the exit apertures is increased. To compensate for any pressure losses along the length of the inner cavity, the size of the radial bores can increase with the distance from the supply point.
In the former embodiment, a housing bore can be connected to the inside of the control slide chamber. The housing bore forms the supply aperture.
According to a second embodiment, the cylinder control slide includes at least one journal which projects from the housing. The journal has an axial bore which forms the supply aperture leading into the inside of the cylinder control slide.
According to an alternative to the second embodiment, at least one housing bore is connected to an annular channel between the control slide chamber and the cylinder control slide. The radial bores start from the annular channel and lead into the inside of the cylinder control slide to form the at least one supply aperture. In this way, the inside of the cylinder control slide is supplied first with medium, via the annular channel. From the inside of the cylinder control slide, the medium again enters the surface groove via the radial bores.
From the following detailed description, taken in conjunction with the drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.